Hydraulically operated mechanical grab



A ril 18, 1967 GUINOT 3,314,709

HYDRAULICALLY OPERATED MECHANICAL GRAB Filed March 24, 1965 2 Sheets-Sheet 1 m M V W I m 7 M 0,. I /|/H///////// \\m AP J Q m mm April 18, 1967 G. L. GUINOT 3,314,709

HYDRAULICALLY OPERATED MECHANICAL GRAB X32506? cum mm ATTOE/Y' VJ United States Patent 3,314,709 HYDRAULICALLY OPERATED MECHANICAL GRAB Gabriel L. Guinot, Le Plessis-Belleville, France, assignor to Societe Anonyme Poclain, Le Plessis-Belleville, France, a French society Filed Mar. 24, 1965, Ser. No. 442,328 Claims priority, application France, Mar. 25, 1964, 968,586 6 Claims. (Cl. 29470) This invention relates to an hydraulically operated mechanical grab of the kind comprising an hydraulic cylinder, a piston slidable in said cylinder, a piston rod connected with said piston and projecting through the lower end of said cylinder, two or more grab members each pivotally connected with the outer free end of said piston rod and each pivotally connected to an arm or link which is in turn pivotally connected with said cylinder, said piston also being provided with a piston rod projecting through the upper end of said cylinder for connection with jib of a crane or the like.

The main advantage of mechanical grabs of this kind is that grab members and the hydraulic cylinder can be rotated relative to the piston about the piston axis. It has however been found that, due to the clearances which have to be provided at the pivotal connections between said grab members and the piston rod and due to the impacts and shocks to which the grab members are sometimes subjected, the pivotal connections between the grab members and the piston rod and indeed to the exposted part of the piston rod itself, tended to become damaged or fractured and such damage or fracture necessitated replacement of the piston and piston rod.

The object of the present invention is to overcome this disadvantage and with this object the invention consists of an hydraulically operated mechanical grab of the kind described wherein the lower piston rod to which the grab members are pivoted is connected with the piston or part of the piston and rotatable about its axis relative to said piston or part of said piston.

In order that the invention may be more clearly understood two particular embodiments thereof will now be described by way of example with reference to the accompanying drawings in which:

FIGURE 1 is a longitudinal axial section of the hydraulic grab showing the grab members in side elevation, and

FIGURE 2 is a similar view to FIGURE 1 of an alternative embodiment.

Referirng now to FIGURE 1 the grab comprises a double acting hydraulic jack 6 including an hydraulic cylinder 10 in which is slidably mounted a piston comprising two separa-ble piston parts 9a, 912, said piston is connected with an upper piston rod 6d, and a lower piston rod 6a. The upper piston rod 6d projects through the upper end of the cylinder 10 and is provided with a substantially U-shaped or forked outer free end 15 by means of which the grab can be attached to the jib of a crane or the like. The lower piston rod 6a projects through the lower end of the cylinder 10 and is provided at its outer free end with a cross arm 3 fixed to said piston rod by means of a nut 7 screwed onto a screw threaded portion 6c of a projection 6b at the end of the piston rod. The projection 61) is of polygonal cross section and is seated in an aperture 3a of corresponding cross-section whereby said cross arm 3 is prevented from rotating relative to the piston rod.

At the ends of the cross arm 3 grab members 1 and 2 are pivotally mounted on horizontal pivots and 4 re spectively and said grab members are each pivotally connected to one end of a link or lever 13 and 14 respectively whilst said links or levers are pivotally connected at their opposite ends to lugs 11 and 12 respectively on the cylinder 10.

The part 9a of the piston 9a, 9b, is integral with the lower piston rod 6a and is connected in axial alignment with the piston part 9b in such a manner that the two parts 90, 9b of the piston are rotatable relative to each other about their axis. For this purpose the upper piston part 915 is provided with an inverted T-section projection 8 which fits into a correspondingly shaped recess in the lower piston part 9a. Thus it will be understood that the two parts 9a, 9b of the piston are securely held together in the axial direction but are capable of relative rotary movement about their common axis and also the cylinder 10 and the grub members 1 and 2 are rotatable about the cylinder axis.

The movement of the piston 9a, 9b within the cylinder 10 for operation of the grab members 1 and 2 is eliected by hydraulic pressure fluid fed into said cylinder through supply pipe lines 16 and 17 and conduits 19 and 18 respectively formed in the upper piston rod 6d. Conduit 18 leads into the top chamber of the cylinder above the piston, and conduit 19 leads into the bottom chamber of the cylinder below said piston. The conduit 19 in the upper piston rod 6d is connected with the bottom chamber of the cylinder through a substantially radial duct 20 in the lower piston rod 6a, said duct communicating with said conduit 19 through a ducted plug member 21 mounted in an axial bore in said lower piston rod 6a, said plug being provided in its external surface with an annular groove or channel 21a connected on one side with a radial bore in said plug leading to the conduit 19 and on the other side with said duct 20 in the piston rod 6a. By this means the piston rod can rotate about its axis relative to said plug 21 whilst maintaining communication between duct 20 and conduit 19.

The embodiment of the invention illustrated in FIG- URE 2 differs from the embodiment according to FIG- URE 1 in that it is provided with a one-piece piston 9 integrally connected with the upper piston rod 6:! and connected with the lower piston rod 6a in a similar manner to that described with reference to FIGURE 1. With this construction the pressure fluid conduit 19 communicates directly with the lower cylinder chamber as shown. The FIGURE 2 embodiment further differs from that according to FIGURE 1 in that the grab members 1 and 2 are pivoted directly to the lower piston rod about a common horizontal axis 22 thus dispensing with the cross arm 3 of FIGURE 1.

The hydraulic grab according to the invention operates in a similar manner to known grabs but in the event of damage or fracture of the lower piston rod 6a said piston rod can be replaced without any need for replacing the piston or other parts of the grab assembly.

It will be understood that the invention is not limited to the particular embodiments herein described but may be modified in various ways without departing from the scope of the invention as defined in the appended claims.

What I claim is:

1. An hydraulically operated mechanical grab comprising an hydraulic cylinder, a piston slidable in said cylinder, a piston rod connected with said piston, the lower part of said rod projecting through the lower end of said cylinder, at least two grab members each rotatable with and mounted on the free end of said lower part of said piston rod in such manner as to pivot about an axis which is transverse to the longitudinal axis of said lower rod part and each grab member pivotally connected with said cylinder, the upper part of said rod projecting through the upper end of said cylinder for connection with the jib of crane wherein said lower part of said piston rod is connected with said upper part of piston rod by connecting means mounted for relative free rotation of said parts of piston rod around their common axis, said connecting means being located Within said cylinder.

2. An hydraulically operated mechanical grab according to claim 1, wherein the piston comprises two separable piston parts relatively rotatable about their axes and the piston rod to which the grab members are pivoted is integral with or rigidly attached to one of said piston parts.

3. An hydraulically operated mechanical grab accord ing to claim 1, wherein each of said grab members is pivotally connected with a cross-arm rigidly secured to the outer free end of the lower piston rod.

4. An hydraulically operated mechanical grab according to claim 1 wherein each of said grab members is pivoted directly to the outer free end of said lower piston rod about a common pivot axis.

5. An hydraulically operated mechanical grab accord ing to claim 2, wherein the two piston parts are rotatably connected together by means of a central T-section projection fitting in a correspondingly shaped recess in the other piston part.

6. An hydraulically operated mechanical grab according to claim 1 wherein said lower piston rod is rotatably connected with the piston by means of a T-section portion formed on said piston rod and engaging in a correspondingly shaped recess in said piston.

References Cited by the Examiner UNITED STATES PATENTS 539,962 5/1895 Seward 294-70 FOREIGN PATENTS 1,136,481 1/1963 France. 1,123,264 2/1962 Germany.

M. HENSON WOOD, 111., Primary Examiner. C. H. SPADERNA, J. N. ERLICH, Assistant Examiners. 

1. AN HYDRAULICALLY OPERATED MECHANICAL GRAB COMPRISING AN HYDRAULIC CYLINDER, A PISTON SLIDABLE IN SAID CYLINDER, A PISTON ROD CONNECTED WITH SAID PISTON, THE LOWER PART OF SAID ROD PROJECTING THROUGH THE LOWER END OF SAID CYLINDER, AT LEAST TWO GRAB MEMBERS EACH ROTATABLE WITH AND MOUNTED ON THE FREE END OF SAID LOWER PART OF SAID PISTON ROD IN SUCH MANNER AS TO PIVOT ABOUT AN AXIS WHICH IS TRANSVERSE TO THE LONGITUDINAL AXIS OF SAID LOWER ROD PART AND EACH GRAB MEMBER PIVOTALLY CONNECTED WITH SAID CYLINDER, THE UPPER PART OF SAID ROD PROJECTING THROUGH THE UPPER END OF SAID CYLINDER FOR CONNECTION WITH THE JIB OF CRANE WHEREIN SAID LOWER PART OF SAID PISTON ROD IS CONNECTED WITH SAID UPPER PART OF PISTON ROD BY CONNECTING MEANS MOUNTED FOR RELATIVE FREE ROTATION OF SAID PARTS OF PISTON ROD AROUND THEIR COMMON AXIS, SAID CONNECTING MEANS BEING LOCATED WITHIN SAID CYLINDER. 